Hypophosphorous acid and hypophosphites as catalyzers of condensation of monoamino monocarboxylic acids



Patented Aug. 14, 1951 UNITED STATES PATENT OFFICE HYPOPHOSPHOROUS ACIDAND HYPOPHOS= 1 s 1 PHITES AS CATALYZERS OF CONDENSA TION OF MONGAMINOMONOCARBOXYLIC ACIDS Michailas Genas, Paris, France, assignor to Socit()rganico, Paris, France, a corporation of France No Drawing.Application August 2, 1948, Serial No. 42,151. In France August 6, 1947.

than 5- carbon atoms, or througho'similar,con-

densation of dicarboxylic. acids with diamines.

The polyamides are highly valuableindustrial products usable in,themanuiacture of ,rnolded articles, films-threads, wires, textile-andmetal coatingsandsimilar uses.

The condensation reactionisetfectedby heate A ing thepolyamidegenerating substance or sub stances. In order to accelerate thereactionj the addition of suitable catalysts has been advocated. Thecatalysts proposed; for that purpose include: substances alkalinein'character such ashy'drated baryta, borax, and sodium bicarbonate;neutral substancessuch as zinc chloride, aluminu nlchlc ride, tinhichloride; and inert substances such as Si i Q -iq *1- 1 .1 w It isknown moreoverthatthe addition of acids to thetreaction mixturearreststhe condensation reaction, as aresult of blockingtheamine func-otion of the aminoacid monomers or polymers, this preventing the reactionfrom proceeding beyond a condensation degree which depends ,on theproportion of acid added to the reaction. a

I have nowv iound, according to, my present invention, that condensationreactions oi the above=d fi ed c a cte mayb c erabl ace celeratedthrough the use,,as* condensation cat; alysts, of V predeterminedproportions ot-phosphorus compounds which are adapted .at thecondensation temperatures togive outhydrogcn phosphide, such ashypophosphorous :acid and the salts thereof: .Thus for vexample,hypophos phorous acid decomposes en heating according was r a cm t 1 I a*ZHsPO eHzPOr-l-PHsf g 7 Similarly ainrnonium hypophosphite decompfisesaccording to the formula I I y I I I 1 2NH4H2PO2- HPO3 +H2O +2NH3+PH3and sodium hypophosphite decomposes accordin to the equation v i c4NaI-I2PO2- Na4P2O7}- 1120+ 2am I f The following examples are givenwiththe intentionmerely of illustrating the procedure -foi e n nt a d al owa clearer understa din the full time ofv the condensation reaction. The

5 Claims. (Cl. 2 60-178) V 6f the iat e iw ut n a y wayame pat s scopethereofj W I Thecondensation tests to be described were effected inab'ulbflask 500 co. in capacity pro; Yidedjfwith three tubulations,placed in a bath of molten salt. jTh jflaskjrwasl providedjwithathermomete d pping 1 .1w the drea h mixture, amechani'cal agitator, anin'let tubeior t e e d n f itro n hc ei to and o let tubeffollowed by adescending refrigerator. 100 gfoif mat rails to be condensed were placedinto the new 1 Lth ei w e e tw h a 5 current of nitrogen fedthrough gthcflask; This current of nitrogen was maintained throughout reaction c wasniaintained at r a suitably selected'tempefature with an errorlefss thanit Zf C, S mple ere ak n a re u ar n r a s and h progress of thecondensation reaction]. was checked by viscosity measurements made onsolutions'icontainin'g ()I5'gfof polymer i'nl'Qi) cc. metares l- The visos t 'no s i t eieefi t d at 20 C. "1111c yiscosity Values wereexpressed by the following equation wherein Lab and ,Lt represent theNapierian logarithms of t andto, which in, turn respective- 1y;designate the times of. how, in seconds .of the solution and of thesolvent in the-same viscosirne eter tube andatthe same temperature, 7

i phosphorous:acid ezgpressed;inrnol per cent-with respect-tatheaminoundecylic acid. The; results o h r s o i m asur m nts e r ineddfined hereinabove are included inl the following tableq Thecondensations were carriedoutat Table I Hypophosphorous acid, mol percent cresol.

plastic mass..-

cresol.

:81 -I 1.43 plastic mass 1.25 Insoluble in meta- 1.47

Insoluble in meta- {3%}plastic mass. Insoluble in metacresol. Plasticmass.

With hypophosphorous acid, up to an amount of about 2 mol percent, anacceleration of the rate of reaction is observed during the first threehours of the condensation reaction, after that however a very sharpincrease in viscosity is found to occur. Over a proportion of 2 mol percent there is first observed, during the first three hours of heating, areduction in the rate of condensation, then a very sharp increase inviscosity up to the point Where products are obtained insoluble inmetacresol and which, at the condensation temperatures used, present theappearance of a plastic mass rather than that of a fused product.

The action of hypophosphorous acid in the first stage of thecondensation reaction probably manifests the accelerating action of theacidic H ion of the hypophosphorous acid when this acid is employed in aproportion up to 2 mol per cent. When more than 2 mol per cent are usedin this first stage, there occurs a slowing down of the reaction due toa stabilizing efiect resulting from blocking of the NHz groups.Thereafter, under the action of heat, the hypophosphorous aciddecomposes according to the equation and it is the PI-Is group whichthen acts to accelerate the condensation in the second stage of thereaction, that is after the end of about 3 hours heating. The differencein physical aspect and the reduction in the metacresol-solubility of thepolycondensate probably correspond with a structural modification of thepolycondensate, which, it is believed, changes from a straight-chainedto a branched or lattice structure.

Ammonium hypophosphite also accelerates the reaction rate, as is shownin the following example. ll-aminoundecylic acid was condensed insimilar conditions as above with 1.2 mol per cent ammoniumhypophosphite; the inherent viscosity values at the end of 1, 3 and 8hours heating respectively were 0.90, 1.22 and 1.89.

With 6. mol per cent ammonium hypophosphite, at the end of as little ashalf-an-hour heating the polycondensate is already found to be in theform of a plastic mass solidifying at ordinary room temperature, butdevoid of any true melting point, in contradistinction from what isfound to be generally the case with straight-chained or filamentarypolyamides, and it does not dissolve in metacresol. Apparently, thepolyamide formed is no longer exclusively formed of straightchained orfilamentary molecules, but comprises at least partially macromolecularlattices. Itis also believed that the change from the filamentary to thelattice structure state is due to the action of the PHa formed bythermal decomposition of the ammonium hypophosphite, as in the case ofhypophosphorous acid.

In the following table, there is set forth by way of a further examplethe progress of the condensation reaction of ll-aminoundecylic acid inthe presence of 3 mol per cent sodium hypophosphite.

The improved accelerating agents described hereinabove are applicable toall kinds of polycondensation or copolymerization reactions capable ofproducing polyamides from aminoacids and mixtures thereof, or fromdiacids and diamines or mixtures of more than one diacid with more thanone diamine, and also mixtures of aminoacids with diacids and diamines.

It will be understood moreover that rather than starting from themonomer materials the accelerator agents of the invention may be used toaccelerate condensation of polyamides from a given degree ofcondensation to a higher degree of condensation.

What I claim is:

1. A method for producing polyamides by polycondensing polycondensablemonoamino monocarboxylic acids containing no other reactive groups intheir molecules, which comprises heating the said materials with asubstance selected from the group consisting of hypophosphorous acid andthe hypophosphites.

2. A method for producing polyamides by polycondensing polycondensablemonoamino monocarboxylic acids containing no other reactive groups intheir molecules, which comprises heating the said materials withhypophosphorous acid.

3. A method for producing polyamides by polycondensing polycondensablemonoamino monocarboxylic acids containing no other reactive groups intheir molecules, which comprises heating the said materials with ahypophosphite;

4. A method for producing polyamides by polycondensing primary monoaminocarboxylic acids containing no other reactive group in their molecules,which comprises heating the said acids with hypophosphorous acid.

5. A method for producing polyamides by polycondensing primary monoaminocarboxylic acids containing no other reactive group in their molecules,which comprises heating the said acids with a hypophosphite.

MICHAILAS GENAS.

REFERENCES CITED Number Name Date Carothers Feb. 16, 1937

1. A METHOD FOR PRODUCING POLYAMIDES BY POLYCONDENSING POLYCONDENSABLEMONOAMINO MONOCARBOXYLIC ACIDS CONTAINING NO OTHER REACTIVE GROUPS INTHEIR MOLECULES, WHICH COMPRISES HEATING THE SAID MATERIALS WITH ASUBSTANCE SELECTED FROM THE GROUP CONSISTING OF HYPOPHOSPHOROUS ACID ANDTHE HYPOPHOSPHITES.